Electrical cut-out



Jan. 8 1924. 133%0325 H. c. SNOOK ELECTRICAL CUT-OUT Filed Sept. 1921 MAM? Patented Jan- 8, 1924.

v UNITED STATES 1,480,225 PATENT OFFICE.

HOMER CLYDE SNOOK, OF SOUTH ORANGE, NEW JERSEY, ASSIGNOR TO WESTERNELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OINEW YORK.

ELECTRICAL cur-our.

Application filed September 8, 1921. Serial No. 499,267.

To all whom it may concern:

Be it known thatI, HOMER CLYDE SNooK, a citizen of the United States,residing at South Orange, in the county of Essex, State of New Jersey,have invented certain new and useful Improvements in Electrical Cut-Outs, of which the following is a full, clear, concise, and exactdescription.

This invention relates to electrical cutouts, and particularly to-thetype of cut-out known as the electrical fuse.

It is customary, in electrical fuses, to surround the fuse conductorwith a packing or filling material such as, for example, plaster ofparis, sand, asbestos, silicic acid, or other suitable insulatingsubstances which will protect the fuse sheath and nearby sub stancesfrom fire or injury upon the premature or delayed disruption of thefusible conductor. It has been found highly desirable, if not absolutelyessential, to pack the filler in a loose and evenly distributed massabout the fuse conductor in order to insure the ready diffusion of theliquid or vaporous metal which is liberated when the fuse blows. The usein electric'fuses of such standard fillers as are mentioned above, nodoubt diminishes the probability of fire due to the heating or explosionof the fuse sheath, but because of the-great amount of filler needed toeffectively quench the electric are which is formed, it is necessary toresort tothe ineflicient and expensive alternative of employing fuses oflarge dimensions.

It is an object of this invention to provide an electric fuse whichemploys a comparatively small amount of insulating filler.

In accordance with its object, the present invention contemplates theuse of a filling material adapted to rapidly adsorb the vapors liberatedwithin the fuse casing when the fuse conductor melts or volatilizes. Ithas been found that silica gel, for example, has the peculiar propertyof readily adsorbing gases because of the very large surface which ithas per unit of volume as compared with other substances, the largesurface being in the form of very fine minute ores.

within the volume of the granules o the gel. Silica gel is an inorganicmaterial and adsorbs or gives oflf gases by a reversible process whichinvolves merely the changing of its temperature.

Another object of the invention is to provide a fuse which is extremelysensitive and which will blow quietly and immediately upon exposure forthe requisite time to the prescribed overload.

It is a further object of the invention to provide a type of fuse whichcan be manufactured in commercial quantities with the desired degree ofuniformity,

Other objects and features of the invention will appear from aconsideration of the following description taken in conjunction with theaccompanying drawing and the appended claims.

The drawing shows a longitudinal view, part 1n plan and part in section,of an electrical fuse of the cartridge type embodying the features ofthe invention. The invention is not limited, however, to this particulartype of fuse.

Referring to the drawing, 1 re resents the fuse conductor, of any suitabe material, such as lead, arranged within a cylindrical casing 2, andattached by soldering or other suitable means to the terminal caps 3 atthe point i. The threaded extensions 5 of the caps 3 are each providedwith a nut 6 as a means for connecting the fuse into an electricalcircuit. The fusible wire 1 is surrounded with loose, dry particles ofsilica gel, shown at 7. The material 7 is a hi hly porous gel of silicawhich ma be formed b mixing an acid, such as hy rochloric aci with asodium silicate solution, forming a colloidal solution of silicic acidfrom which the silicious compound sets to a el. The concentrations ofthe acid and so ium silicate solution must be carefully determined, andcare must be taken in bringin' the two together in order to prevent arapi coagula tion due to the instability of the mixture.

andwashed free from acid and salt. The

water must be very carefully and slowly removed from the washed gel inorder that the finished product'may retain the highly porous structurewhich is exhibited by the gel while in solution. To accomplish this, thematerial may be subjected to gradually increasing degrees of heat inorder that no sudden change may take place. It is to the arcs forme lidstructure that silica gel owes its remarkable propert of adsorptionwhich is not 'dis' played y ordinary silicic acid or other fuse fillers.For the purposes of the present in vention silica gel has been found tobe more effective in quenching the electric are formed in the fuse ifthe granular gel is activated by drying in open air or in a partialvacuum The particles of silica l are full of pores and capable of adsorliing gases rapidly and may serve two general -functions in the sto pingor quenching of electric within the fuse casing. One of these functionsis that of the adsorption of the un-ionized or non-conducting metallicvapors surrounding the conducting arc and which have been vaporized fromthe surface of the fuse conductor by the heat liberated upon the blowingof the fuse. By this adsorption of the un-ionized or non-conduct-- ingmetallic vapor there is removed from the area of the conducting streamof the arc metallic vapor which otherwise might furnish material whichcould be further ionized or rendered conducting and thus assist theconducting are stream to persist. It is possible that the adsorption orabsorption of these metallic vapors is materially assisted by thethermal capacity of the gas adsorb-.

ingv material, which in the case of silica gel is extremely high.Another function which this filling material may perform because of itsorous nature and the large surfaces which 1t presents to gases or vaporsis that of causing charged carriers of opposite signs existing in arcstreams to come together and discharge their electric charges, thusrendering the arc stream non-conducting. It is well known thatoppositely charged carriers in partially conducting gases combine andare discharged, due to the passage of the gases through porousmaterials. The use of silica gel as a filling material thus insuresprompt blowing at the intended maximum capacity of the fuse, it beingimpossible for the liberated gases to form with the gel an independentconducting path for the current, as often happens when inefficient ordefective fillers are used.

Because of the extremely large-surface in r the form of very fineporesin the particles of silica gel as compared to all other fillersheretofore used, it will be evident to those skilled in the art that amuch smaller fuse may be used than has heretofore been pos-v and henceeliminating the danger of injury to nearby substances.

It is not intended to limit the invention to the use of a fillingmaterial of silica gel, since any other material having highlyadsorptive properties may also be used.

, What is claimed is LAn electric fuse having a filling materialcomprising a gelatinous gas adsorbing material.

2. An electric fuse having a filling materiai consisting of silica gel.

3. An enclosed electric fuse having its fuse conductor surrounded byloose, dry particles of silica gel.

. 4. An enclosed electric fuse of the cartridge type having its fuseconductor surrounded by loose, dry granular silica gel.

5. An electric fuse having its fuse conductor surrounded by loose, drygranular silica gel which has been activated.

In witness whereof, I hereunto,subscribe my name this 6th day ofSept. A.D, 1921.

HOMER CLYDE SNOOK.

